It is official! Windows Vista Service Pack 1 (SP1) was released to the download center and Windows Update as well as to the download center on microsoft.com today. Note that this release only includes the English, French, Spanish, German and Japanese versions.
In mid-April, Windows Vista SP1 will be released to Windows Vista customers who have chosen to have updates downloaded automatically and will be a much smaller download, advisable for people with only one computer to update or on a dial up connection.
Note that you will need to have the prerequisites before being able to install SP1.
Although the announcement indicated that SP1 would be released in mid-April to customers who have chosen to have updates downloaded automatically, apparently this has changed. Either that or different update settings (i.e., ask and let me decide as I have) started receiving the SP1 install offer via automatic updates last evening.
I received it today. Being on dial-up, the 69.8 MB download is taking quite a while. I will likely have to leave it running when I head off to bed and see how it does on its own.
For more information on what to expect, see Ed Bott's writeup: Want Vista SP1? Here’s what to expect. In particular, note the link to the Microsoft dedicated support page for Windows Vista SP1.